Recently, wireless communication systems such as IEEE802, 11a/b/g are widely employed. These are communication systems having an equivalent wireless function substituted for Ethernet (registered trademark) that is called wireless LAN (Local Area Network) system and used for cable LAN system.
A wireless LAN system was initially used for a pocket or portable personal computer and a portable wireless terminal device. After that, the range of use expanded to various fields, and for example, in order to eliminate the complication of wiring cables, a wireless LAN system has been proposed for terminal devices whose using place is fixed.
As an example of its application, conventionally proposed is a technology of using a wireless LAN system for video and audio contents distribution service in aircrafts (for example, refer to Patent document 1).
In this example, a wireless LAN system is installed in an aircraft, and contents data is delivered to a wireless terminal device mounted in each passenger seat, thereby realizing information distribution service for which the wireless LAN system is used. Such a distribution system is configured in that contents data offered to users is accumulated in a server of the system, and a plurality of wireless access points (hereinafter called access points) serving as wireless base station equipment connected to the server are installed in the aircraft. Also, a wireless terminal device is installed in each seat, and the position of each access point is set so that one access point covers a plurality of wireless terminal devices. As an access point setting method, the interior space of the aircraft is divided into a plurality of small areas, and the access points are respectively allocated to the service areas in the aircraft so that one access point corresponds to one small area. In this example, each small area is partitioned by using a working area as a boundary such as a kitchen that is called a galley where cabin crews offer services. Many of the galley walls are made by using a material such as metal or carbon composite material that is an obstacle to radio wave propagation, forming an electromagnetic shield structure. Also, a toilet or the like having walls made by using the above-mentioned material is often disposed in the vicinity of the gallery or as a part of the galley. Therefore, structures having an electromagnetic shield structure such as a galley and toilet are generally called galley in the following description.
As a countermeasure for interference between wireless terminal devices, a directional antenna is disposed at each access point so that radio waves are radiated without giving interference or disturbance to other small areas as much as possible, and it is set for wireless communication with each wireless terminal device within its area by using a predetermined channel. It is configured in that communication is established between one access point and each wireless terminal device within its small area through time division of frequency band of the channel, and thereby, it is possible to individually provide information distribution service to a plurality of wireless terminal devices by using one channel.
As for wireless communication, there are conventionally disclosed methods such as a method of making radio waves reflected from wall surfaces between wireless base station and wireless terminal and a method of enhancing communication efficiency and antenna efficiency by dividing electromagnetic wave components such as vertically polarized wave and horizontally polarized wave to be used (for example, refer to Patent documents 2 to 4).
However, in the case of communication between a cabin crew and a passenger or between cabin crews in an aircraft, the cabin crew is moving in the aircraft or working in the galley in many cases. In case the cabin crew is moving, it is possible for the crew to make communication by using a portable wireless terminal device because of an access point that covers a wide area. However, when the crew is in a galley or the like, it is difficult to establish stable wireless communication because the outer surfaces of the galley reflect the radio waves. Accordingly, the conventional method is such that a cabin crew uses a plurality of cable communication terminals installed at fixed portions to make communication with other cabin crew or passenger. As a result, there arises a problem that it is necessary for the cabin crew each time to move for communication to a place where a cable communication terminal is installed, and it is rather troublesome and also results in being late in contacting in case of emergency.